So I wear a pair of OluKai 'Ohana Flip-Flops that I purchased from REI, they are amazing and actually have arch support and are water proof. If you prefer sneakers then I recommend using body glide (it is used for anti-chaffing anywhere including your feet). I'd also use baby powder in the socks to help absorb moisture and then a pair of running socks or smart wool socks. I've run a 50 K (31 mi) without getting blisters using this technique and before doing this I'd get tons of blisters just walking for a day. Also buy shoes like a runner would if you do sneakers, i.e. a 1/2 size up from your regular size; that way you have room if your feet swell. Finally, I'd recommend going to a specialized running store (you should be able to get walking shoes as well) or a store like REI to be fitted. Those sales people sell shoes to people that plan to wear them all day (either to hike or run in) so they will be able to size you correctly and steer you to the correct shoe. The hiking boots I got from REI years ago are great, in part because the sales person talked to me about what I was feeling when I tried them on and examined my foot carefully, determined that I have a high arch, and steered me towards the type of arch support I need for my boots.
But if you are going when it is warm then the OluKai 'Ohana Flip-Flops or Keen sandals, etc. Those will just be better for the rain that comes but that's my opinion.
Oh and extra socks and tape for your feet if you decide on sneakers, even if it doesn't rain switching socks out helps as well! (tape is better then a band-aid; again a specialty store can assist you with picking the correct supplies)